Process for production of lubricating oil



Jan. 22, 1935. u. B. BRAY El AL 8 PROCESS FOR PRODUCTION OF LUBRICATING OIL 4 Filed Aug. 4, 1951 4 Sheets-Sheet 1 200 TEMPERATURE- F'AHRENHEIT 0G) ggs g N? "IVSHEIAI N n 1.10 HAYS M1900 91A INVENTORS U/rzi: 5.132" Q CIaudeESM'ff u. B. BRAY El AL 1,988,711

PROCESS FOR PRODUCTION OF LUBRICATING OIL Filed Aug. 4, 1951 4 Sheets-Sheet 2 snommafiemsmamovmcmmomm on on 8 on Qw cm .Jan. 22, 1935.

w mw "IVSHL'IAINO .L'IOHAVS 'MIs'oQsm INVENTORS U/r/c'BBrqy Claude EJ5102 1? Jan. 22, 1935.

4 Sheets-Sheet 3 Filed Aug. 4, 1951 m w S mm om m Ed 1 mm Y Wu 0 NA mm U \R v 8 f [J W A 1% mm E. Y L m..n. B B -m m@ 1| M F E \x Q\ v .mvm, Q\ JUN.) L mm 3 wm Iv m Q NQ 4%. e a. mm 4 MK MN hm N 1 T vh E ow k n mm ww vm.\ g Q Jan. 22, 1935. B, BRAY AL 1,988,711

PROCESS FOR PRODUCTION OF LUBRICATING OIL Filed Aug. 4, 1931 4 Sheets-Sheet 4 INVENTORS Ulric fifirgl 4? Claude .J'mfi.

Patented Jan. 22, 1935 rnoouss FOR rnonuo'rlou or wsnrca'rmo on.

Ulric B. Bray, Palos Verdes Estates, and Claude 11.

Swift, Huntington Park, Calif assignors to Union Oil Company of California, Los Angcles, CaliL, a corporation of Cal fornia I npplication August 4, 1931, Serial No. 555,016 14 Claims. (01. 196-37) This invention relates to a. method and apparatus for treating petroleum to produce lubricating oil.

One of the distinctive characteristics of a lubricating oil is its viscosity. For many purposes lubricants are preferred which exhibit a minimum variation in viscosity with variations in temperature, i. e. have low viscosity temperature susceptibility. It is generally known that the viscosity of lubricating oil produced from Western crude such as California naphthene base crudes,

that is, crude containing asphalt, varies more with change in temperaturethan do lubricating oils produced from parafiin base crudes. That is,

13 if two such oils have the same viscosity of 100 F.,

the Western oil will have a much lower viscosity at 210 F. than will the pamflin base oil. This change in viscosity with temperature is sometimes called the temperature susceptibility of an oil. lubricating oils that they are distillates, that is, are vaporized from crude oil and condensed. Lubricating oils produced from paraffin base oils, containing substantially no asphalt, are general- I ly produced by first distilling light oils overhead including the kerosene and gas-oil and also taking overhead light lubricating oils called neutrals" having a viscosity in the neighborhood of 100-200 seconds, Saybolt universal at 100 F., leaving an undistilled residue termed bright stock. The oils of various viscosity are made by blending these neutrals and bright stock in any desired proportion to obtain the desired viscosity. This variation in viscosity with temperature can be best illustrated by reference to Fig. 1. This chart is well known and is described and shown in the International Critical Tables, Vol. 2, page 147. It is a special type of temperature coordinate chart in which the abscissa scale is the logarithm of absolute temperature and the ordinate scale is an additive function of the viscosity which has been developed experimentally. The resulting ordinate scale is a warped logarithm scale of the kinematic viscosity upon which, for convenience, the corresponding scale of Saybolt universal viscosity has been superimposed. It is found as an experimental fact, that the viscosity of any petroleum oil for varying temperatures willfall on a straight line when plotted on this chart. The steeper the slope of the line, the greater is the variation at the viscosity with temperature.

Lubricating oils produced by distillation from asphaltic crudes, containing no wax, have ap- It is one of the characteristics of Western proximately the same slope on this chart, inde-.

pendent of the viscosity of the oils at any giventemperature. Thus, an oil having a viscosity corresponding to 600 seconds Saybolt universal at 100 F. willhave approximately the same slope as an oil having a viscosity of 1000 seconds Saybolt 5 universal at 100 F. Acid treatment of these oils has a tendency to flatten the curves, i. e. making them less steep. The amount or flattening will depend upon the degree of treatment. We have found, however, that all commercial western 1'11.- 10 bricating oils have substantially the same slope. curve B of Fig. 2 illustrates the curve for a treated oil of the asphalt base type having Saybolt universal viscosities of 600 seconds at 100 F. and seconds at 210 1?.

Likewise residual lubricating oils produced from paraffin base crude oils, containing substantially no asphalt will have substantially the same slope on this chart independent of the viscosity of the oils at any given temperature. However, as the 20 viscosity of the residuum varies from 2000-5000 seconds Saybolt universal at F., the slope will vary from 2 to 5%. The particular bright stock shown in curve A of Fig. 2 has Saybolt universal viscosities of 2350 seconds at 100 F. and seconds at 210 F.

That property possessed by certain components of an oil which imparts to it a slope approachin curve A of Fig. 1 maybe said to be a measure of theparafiin base characteristics exhibited by the oil.

It has been observed by one of us that many oils containing asphalt are mixtures of hydro carbons analogous both to the hydrocarbons: present in paraflin baseoils and those present in asphalt base oils. It has further been observed by one of us that during the heating of an oil containing asphalt, the asphalt apparently induces certain chemical and perhaps certain physical reactions at relatively low temperatures which tend to destroy the inherent low viscosity temperature susceptibility of the lubricating oil fractions. This apparent catalytic phenomena seems to explain the observed changes although we do not wish to be understood as being bound by this 4 theory. It has been observed that these temperatures at which the changes appear are below the vaporizing temperatures in batch distillation vacuum or steam) of the lubricating. oil fractions which have Saybolt universal viscosities 50 above 400-500 seconds at 100 F. It is safe to say that no oil containing asphalt can be topped to the point where fractions above 400-500 seconds, Saybolt universal viscosity at 100 F. are vaporized without a degeneration of those char- 55 iii:

acteristics of the paraflin hydrocarbons which impart to the oil a low temperature viscosity susceptibility. During the distillation of the heavy oils in the presence of asphalt some change in molecular structure or configuration takes place which is attended by a change of viscosity temperature characteristics. This behavior is thought to be due to pyrolytic reactions which are catalyzed by the presence of asphalt. The above discovery is made the subject matter of application; Serial No. 466,189. The lubricating oil components in the crude oil which have high parafiln base characteristics, i. e., similar to the oil represented by curve A of Fig. 1, are converted by the distillation into oils exhibiting low paraffln base characteristics, i. e., similar to the oil represented by curve B of Fig. 2.

In order to preserve the inherent characteristics of the lubricating oil components of crude oil containing asphalt which are impaired by distillation methods as previously described, we have, in accordance with the process of the above application, caused the separation of the oil from the asphalt by a method wherein the lubricating oil constituents present in the crude oil are separated from the asphalt present in such a manner that the oil retains those characteristics which it possessed in the original crude oil. As a means of attaining this end, it has been found advisable to cause the separation of the asphalt.

from the oil by means of solvents which are capable of dissolving the oil and which do not dis solve the asphalt. Such solvents are light petroleum fractions, such as naphtha, casinghead gasoline and petroleum fractions normally vaporous at ordinary temperature and pressure. Other solvents which may be used are alcohol, ether, mixtures of alcohol and ether, acetone, etc. We prefer to use as our solvent a petroleum fraction obtained by the rectification of natural gasoline. For most purposes a fraction composed of 6.72% ethane, 72.20% propane, 19.91% isobutane, and 1.17% normal butane is satisfactory. However, by using a. fraction containing a higher percentage of ethane it is possible to produce a lubricating oil having a low Conradson carbon value. Such a fraction would contain ethane varying in quantities from 4.0 to 50 per cent by volume. It

will be understood, however, that these merely illustrate the types of fractions which may be used and that the compositions may vary. This fraction will hereinafter be referred'to as propane for purposes of simplicity.

In carrying out the extraction of the oil with this light liquid fraction the solution is maintained at a pressure suflicient to maintain "the propane liquid at ordinary temperatures. The fraction described above is liquid at ordinary temperatures at a pressure of about pounds per square inch. The extraction, of the oil from the petroleum at such pressures results in an asphalt substantially free of oil composed chiefly of pure bitumen and a solution of oil in the liquid petroleum fraction. The oil dissolved in the liquid propane contains substantially all of the lubrieating oil components which are present in the crude oil and in substantially the same form as they exist in the original crude oil.

Before further discussion of this invention, it will be best to define a new term whch we have found useful in identifying the oils of our invention. Curve C of Fig. 1 represents a typical oil which has been extracted with propane from oil containing asphalt. curve has a slope intermediate between curve A and curve B,

i. e. a true paraflin base bright stock, having for example, Saybolt universal viscosities of 2350 seconds at 100 F. and seconds at 210 F., and a true Western lubricating oil having for example, Saybolt universal viscosities of 600 seconds at 100 F. and 55 seconds at 210 F. Since the slopes of A and B are characteristic of all oil of like nature, the absolute viscosity is immaterial to our present purpose after the lines are once defined. We draw two lines on the chart parallel to curves A and B, respectively,

passing through the intersection of curve A with.

the 100 F. line. Thesecurves are defined as curves A and B. The distance between their intercepts on the 210 F. temperature ordinate line is taken as 100. The ratio of the intercept between curves C and B and the intercept between A and B gives the paraffin base characteristics of the oil corresponding to curve C. It will be observed that the curve C shows 22% paraifin base characteristics.

We have discovered that many lubricating oils obtained by extraction with solvents, for instance, propane, from crude oil containing asphalt are comppsed of oils which are high in parafiin base characteristics, i. e., have slopes approaching curve A of Fig. 1, and oils low in paraflin base characteristics, i. e., have slopes approaching curve'B of Fig. 1 and that these oils may be separated into oils which exhibit a low temperaturewiscosity susceptibility resembling oils produced from non-asphalt containing crude and oils which exhibit a high temperatureviscosity susceptibility corresponding to oils produced by distillation. For convenience, we will call the oils which have high parafiln base characteristics parafiinoid and those which have low paraffin base characteristics and resemble the western lubricating oil distillates nonparaflinoid". The propane extract which consists of such a mixture of parafiinoid and nonparaffinoid oils may be separated into these respective oils by the use of solvent agents which will selectively dissolve out the non-parafiinoid components. We have found that certain solvents have a selective solvent action for the nonparaffinoid oils. As solvent agents which will efi'ect this separation, we have found liquid sulphur dioxide, mixtures of acetone and benzol, aniline or methyl formate useful. Acetone alone in addition to being an asphalt precipitant also has in some measure the ability to split the oil the above manner. ihe use of liquid sulphur dioxide hasjbeen found especially valuable as a solvent to separate the propane extract into oils which exhibit high paramn base characteristics and into oils which exhibit low parafiin base characteristics. By subjecting the propane extracted oil to the selective solvent action of liquid sulphur dioxide, it is possible to separate this material into oils which have a low temperatureviscosity susceptibility and oils which have a high temperature-viscosity susceptibility.

As a further means of improving the temperature viscosity susceptibility of the oil, we may treat it with sulphuric acid. Such treatment removes from the oil a portion of the bodies present which possess a high temperature viscosity susceptibility. Elie topped oil is first dissolved in liquid propane in order to separate the oil from the asphalt. -The propane solution of oil is then agitated with treating quantities of sul phuric acid after which the sludge formed is allowed to settle out; The propane is then separated from the acid treated oil, after which the oil is cooled and treated with liquid sulphur dioxide to resolve it into a portion exhibiting high paraflin base characteristics and a portion exhibiting low paraflin base characteristics.

While the above method of treating the oil with acid appears to be preferable from the standpoint of economy; we have found that by performing this step in the process subsequent to treatment with liquid sulphur dioxide that more effective results are obtained. By acid treating the oil prior to extraction with liquid sulphur dioxide, a large portion of the acid is consumed in removing from the oil unsaturated bodies which are easily removable with liquid sulphur dioxide. By treating the oil with acid subsequent to extraction with liquid sulphur dioxide, the acid utilized in such treatment is free to act upon those undesirable bodies present in the oil which are not removable by liquid sulphur dioxide. Thus, by acid treating subsequent to extraction with sulphur dioxide, we are able to obtain a more economical use of acid and a more effective removal of undesirable bodies present in the oil.

One of the desirable qualities of a lubricating oil is a low Conradson carbon value. According to the U. S. Dept. of Commerce,'Bureau of Mines Tech. Paper 323-B, this value is intended to throw some lightupon the relative carbon forming propensities of an oil. Oils which possess a low value have less tendency to cause carbon deposition in internal combustion motorsduring use than 'do oils which possess a high value. In general, lubricating oils produced by the ordinary distillation processes from crudes cotaining asphalt exhibit a low Conradson carbon value whereas lubricating oils produced from paraflin' base crudes exhibit a high value.

It is one of the characteristics of the lubricating oil produced by our process that it possesses a low Conradson carbon value. In Table 1, Conradson carbon'values are shown for a typical paraflin base lubricating oil, a typical asphaltic base lubricating oil and a typicaloil produced by our process.

TABLE I Conradson carbon values Generally stated, it is the object of our invention to isolate from crude oil those oils having characteristicswhich impart to it the low temperature-viscosity susceptibility typical of paraffin base oil.

More particularly it is an object of our invention to isolate from asphalt containing oils those components which impart to the oil the reduced susceptibility to change in viscosity with temperature which is characteristic of oils obtained from non-asphalt containing oils; that is. to sepstrate the parafilnoid from the non-parafllnoid components 0! the asphalt containing crude oils.

It ismore particularly an object of our invention to isolate from asphalt containing oils those lubricating oil components which we call paraf-' finoid and which resemble the lubricating oils produced from petroleum crudes mbsta ntlally free of asphalt but to conserve those peculiar properties of asphalt crudes which impart to the lubricating oils obtained therefrom a relatively low Conradson carbon .value as compared with oils produced from paraflin base crudes.

It is a further object ofour invention to precipitate asphalt from an oil containing asphalt with liquid propane and thereafter to extract oil with liquid sulphur dioxide with an end in view of obtaining an oil relatively insoluble in liquid sulphur dioxide and which is free from asphalt and which has characteristics resembling oils produced from crudes substantially free of asphalt.

Itis a further object of our invention to isolate from asphalt containing oil those lubricating oils which exhibit a relatively low viscosity temperature susceptibility and which possess a relatively low Conradson carbon value.

The process will be more adequately understood by referring to the. drawings.

Fig. 1 is a set of curves representing temperature viscosity relationships of an oil produced by extraction from an asphalt containing oil.

Fig. 2 is a set of curves representing temperature viscosity relationships of an oilproduced by treatment of the oil shown in Fig. 1 to remove fractions which increase its temperature-viscosity susceptibility. I

Fig. 3 is a schematic arrangement of one form of the apparatus in which our process may be carried out.

Fig. 4 is a schematic arrangement of another form of the apparatus in which our process may be carried out;

Referring more particularly to Fig. 3, the crude oil from which there has been removed all of the gasoline, kerosene and gas oil in tank 1 is sent by means ofpump 3 to line 4 where it meets a stream of propane coming from tank 10 throughvalve l1, pump '98 and line 12. The mixture of propane and topped oil passes into chiller 5 where the temperature of the mass is lowered by allowing a portion of the propane. to vaporize through valve 66 into line 67 which is sent by compressor 9'? to condenser 19 where it is liquefied and sent by line 20 to propanestorage tank 10.

The cooled mass in chiller 5 passes by means of line 6 to agitator 7 where it is thoroughly mixed and is sent by means of line 8 to decanter 9 where the asphalt is allowed to separate out and is withdrawn through valve 52 and line 53. It is sent by means of pump 54 through line 53 to heater 55 where the temperature of the mass is raised sufliciently to vaporize all propane and moisture present. The heated mass passes from heater 55 through line 56 to separator 57 where the asphalt separates outand is wihdrawn through valve 58 and'passes by means of line 59 to asphalt storage 60. The propane and water vapor in separator 57 pass through line 61 to con-- denser 62 where the water vapor is condensed. The mixture of water and propane vapor passes through line 63 to separator 64 where the water is separated out and removed through valve]! and line 72. The propane vapor in separator 64 passes out through line 65 to compressor @100 where it is compressed and sent by means of line -to condenser 19 where it is liquefied and passes by means of line 20 to storage tank 10.

The propane solution of oil in decapter 9- is withdrawn through line 73 and mixed with sulphuric acid coming valve 75, pump 76 and line 77. The mixture of acid and oil-is thoroughly mixed in agitator 78' from storage tank 74 through the sludge is permitted to settle out. The sludge in decanter 80 is removed through valve 81 and sent by means of pump 82 through line 83 to heater 84 where the temperature is raised to a point sufliciently highto vaporize any propane contained therein. The heated mass passes by means of line 85 to separator 86 where the sludge separates out and is removed through valve 87 and sent by means of line 88 to storage tank 89. The propane vapor in separator 86 passes through line 90 to scrubbing tower 91 where it is contacted with liquid caustic soda in'order to'remove any sulphur dioxide present. The scrubbed propane vapor passes from tower 91 through line 95 to compressor 101 where it is compressed and is sent by line 95 to condenser 19 where it is liquefied and sent by means of line to propane storage tank 10.

The acid treated oil dissolved in propane is removed from decanter 80 through line 96 and passes through clay tower 97 to remove any remaining sludge particles present. The sludge free oil'passes from tower 97 through line 13 to pump 68 which forces it into evaporator 14 where by aid of steam introduced through closed steam coil 21 all of the propane in the oil is vaporized and passes by means of valve 15 through line 16 to compressor 99 where it is compressed and sent to condenser 19 where it is liquefied and passes by means of line 20 to storage tank 10. The propane free oil in evaporator 14 is removed through valve 22 and passes by means of line 23 to pump 24 which sends it through line to cooler 26 where the temperature of the oil is lowered sufficiently for extraction with liquid sulphur dioxide. The'cooled oil from cooler 26 passes by means of line 27 to the lower zone of extraction column 28. Liquid sulphur dioxide from storage tank 29 passes through valve 102 in line and is sent by means of pump 31 through line 30' to the upper zone of extraction column 28 due to the diiference in the specific gravity'of the oil introduced into the lower zone of the'extraction column and the liquid sulphur dioxide introduced into the upper zone of the extraction column, these two liquids tend to separate. As the liquid sulphur dioxide passes down through the ascending column of oil it dissolves certain components present. This solution of oil in sulphur. dioxide is removed through valve 70 and passes by means of line 34 to evaporator where the sulphur dioxide present is vaporized with the aid of steam introduced through closed coil 41 and is removed through valve 36 and line 37 to compressor 38 where it is compressed and sent by means of line 37' to condenser 39 where it is liquefied and passes by means of line to sulphur dioxide storage tank 29. The sulphur dioxide free oil in evaporator 35 is removed through valve 42 and sent by means of line 43 to storage tank 44.

The ascending column of oil in extraction column 28 passes through valve 105 into line 31 to auxiliary separator 32 where any remaining liquid sulphur dioxide is separated out. The clear oil in auxiliary separator 32 is removed through'line to evaporator 46 where the sulphur dioxide present is vaporized with the aid of steam introduced through closed coil 48. The sulphur dioxide vapor is removed from evaporator 46 through valve 47 and sent by means of line 37 to compressor 38 where it is compressed and passes by means of line 37' to condenser 39 where it is liquefied and passes by means of line 40 to sulphur dioxide storage tank 29. The sulphur dioxide tree oil in evaporator 46 is removed through valve 49 and passes by means of line to refined oil storage tank 51.

Referring more particularly to Fig. 4, this embodiment relates to the process in which a modification is made whereby the acid treatment is performed subsequent to the extraction of liquid sulphur dioxide.

The residual oil passes byvalve 2 to pump 3 where it is forced into line 4 and meets a stream of liquid propane coming from storage tank 10 through valve 11, pump 8 and line 12. The mixture of propane and topped oil passes from line 4 into chiller 5 where the temperature of the mass is lowered by allowing a portion of the propane present to vaporize through valve 6 into line 7 where it is sent by means of pump 106 to condenser 9 where it is liquefied and passes into propane storage tank 10. The cooled mass in chiller 5 passes by means of line 13 to agitator 14 where it is thoroughly mixed and passes by means of line 15 to decanter 16 where the asphalt is allowed to settle out.

The separated asphalt in decanter 16 is removed through valve 17 and sent by means of pump 18 through line 19 to heater 20 where the temperature of the mass is raised sufficiently to vaporize all moisture and propane present. The heated mass passes from heater 20 through line 21 to separator 22 and the asphalt separates out and is removed through valve 23 and sent by line 24 to asphalt storage tank 25. The water vapor and propane in separator 22 passes by means of line 26 to condenser 27 where the water vapor is condensed. The mixture of water and propane passes through line 28 to separator 29 where the water is removed through valve 30 and line 31. The propane vapor in separator 29 passes through line 32 to compressor 104 where it is compressed and sent to'condenser 9 where it is liquefied and p sses into propane storage tank 10.

e propane solution of oil in decanter 16 passes by means of line 33 to evaporator 34 where the propane is vaporized with the aid of steam introduced through closed coil 35 and passes through valve 36 and line 37 to compressor 107 where it is compressed and sent to condenser 9 where it is liquefied and passes into propane storage tank 10.

By proper adjustment or the quantity of steam introduced through line 35, all of the propane present in the oil may be vaporized at a temperature sufiiciently low for subsequent sulphur dioxide extraction of the oil.

The propane-free ofl in evaporator 34 is removed through valve 38 and passes by means of line 39 to pump 40 where it is forced through line 41 into the lower zone of extraction column 42. The liquid sulphur dioxide in storage tank 43 is withdrawn through valve 44 and sent by means of pump 45 through line 46 into the upper zone of extraction column 42. Due to the difi'erence in specific gravity of the oil introduced into the lower zone. of the extraction column and the liquid sulphur dioxide introduced into the upper zone of the extraction column, these two liquids tend to separate. As the sulphur, dioxide passes down through the oil it dissolves certain components present which are removed in the form of a sulphur dioxide solution through valve 47 and pass by means 01' line 48 into vaporizer 49 where the sulphur dioxide is vaporized with the aid of steam introduced through closed steam coil 50 and passes from vaporizer 49 through line 54 to compressor 55 where it is compressed and is sent tocondenser 56 where it is liquefied and evaporator 49 passes through valve 51 to line 52' where it is sent to extract storage tank 53.

The ascending column of oil in extraction column 42 from which the liquid sulphur. dioxide soluble components have been removed passes by means of line 58 to auxiliary settling chamber 59 where any remaining liquid sulphur dioxide is allowed to settle out. The sulphur dioxide free oil in settling chamber 59 is removed through line 61 into evaporator 62 where the sulphur dioxide is vaporized by means of steam introduced into closed coil 63 and passes by means of line 54 to compressor where it is compressed and passes to condenser 56 where it .is liquefied and passes by means of line 57 to storage tank 43.

The sulphur dioxide free oil in evaporator 62 passes through valve 64 into cooler 65 where the temperature is lowered suficiently for acid treatment. The cooled oil from cooler 65 issent by means of pump 66 to line 67 where it is re-dissolved, the liquid propane coming from storage tank 10 through valve 90, pump 105 and line 91. The mixture of oil and propane is mixed with sulphuric acid coming from storage tank 68 through valve 69, line 70 and pump 71. The mixture cf oil and acid in line 67 passes into agitator '72 where it is thoroughly mixed and then passes by means of line 73 into settling chamber '74 where the sludge is allowed to settle out.

The sludge in separator 74 is removed through valve '75 and sent by means of pump '76. through line 77 to heater 78 where the temperature is raised sufilciently to vaporize all of the propane present in the sludge. The heated mass emerges from heater '18 through line 79 and passes into separator 80 where the sludge separates out and is removed through valve 81 and line 82 to sludge storage tank 83.

The propane vapor in separator 80 which is contaminated with sulphur dioxide passes by means of line 84 to scrubbing tower 85 where it is contacted with a solution of caustic soda to remove the sulphur dioxide. The scrubbed propane vapor passes from tower 85 to pump 1 03 where it is compressed and sent by means of line 89 to condenser 9 where it is liquefied and passes into propanestorage tank 10.

The acid treated oil in settling chamber '74 passes by means of line 92 to clay tower 93 where any remaining sludge is removed. The sludgefree oil dissolved in propane passes by means of line 94 to evaporator 95 where the propane is vaporized with the aid of steam introduced through closed steam coil 96 and passes by means of valve 100 and line 101 to compressor 102 where it is liquefled and sent through line 89 to compressor 9 where it is liquefied andpasses into propane storage-tank 10.

The refined 011 in vaporizer 95 is removed through valve 9'7 and by means of line 98 into refined oil'storage tank 99.

As illustrative of the operation of the process upon one type of oil and without intending to limit our invention, the following is an example:

Topped oil in tank 1 of Fig. 3 at a temperature of about 200 F. is mixed with liquid propane and cooled by allowing a portion of the propane pres cut to vaporize to a temperature, thus reducing the temperature to about 1". after which it is thoroughly mixed in agitator I. The thoroughly agitated mass passes into decanter 9 where the propane solution'of lubricating oil is separated from the undissolved asphalt. This oil dissolved in liquid propane which mixture of paraflinoid and non-parafiinoid oils possessing 22% paraflin base characteristics is further purified by treating it with sulphuric acid introduced from tank '74. The propane present in the acid treated oil is then removed by distillation after which the oil is chilled to about 20 F. and then subjected to treatment with liquid sulphur dioxide for the purpose of separating the paraflinoid components from the non-paraflinoid components. That portion of the oil which is insoluble in the liquid sulphur dioxide contains the paraflinoid constituent. Curve C of Fig. 2 is representative of an oil obtained by our process and exhibits 62% paraiiin base characteristics.

The foregoing exemplary description is merely illustrative of a preferred mode of carrying out our invention and is not to be taken as limiting, as many variations may be made within the sccpe of the following claims by a person skilled in the art without departing from the spirit thereof.

We claim:

l. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent to separate asphalt. removing the asphalt from the oil and solvent, removing the solvent from the oil, extracting said substantially asphaltfree oil with a selective solvent to form a parafflnoid fraction and a non-paraflinoid fraction and separating said fractions.

2. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent to separate asphalt, removing the asphalt from the oil and solvent, separating the solvent from the oil, extracting said substantially asphalt free oil with liquid sulphur dioxide to form a paraiiinoid fraction and a non-paraflinoid fractioii and separating said fractions. I

'3. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied hydrocarbon solvent containing a major portion of propane to separate asphalt, separating the asphalt from the oil and solvent, removing the solvent from the oil, extracting the substantially asphalt free oil with a selective solvent to form a parafllnoid fraction and a non-paraflinoid fraction and separating said fractions.

4. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent consisting mainly of ethane and propane to separate asphalt, separating the asphalt from the oil and solvent, separating the solvent from the oil, extracting the substantially asphalt'free oil with a selective solvent to form a paraflinoid fraction and a non-paramnoid fraction and-separatin said fractions.

5. A process as in claim 4 in which the selective solvent is sulphur dioxide.

'8. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent, containing a'maior portion of hydrocarbons of less than four carbon atoms to separate asphalt,

separating the asphalt from the oil and solvent, removing the solvent from the oil, extracting the substantially asphalt free oil with a selective solvent to form a paramnoid fraction and a nonparaflinoid fraction-and separating said fractions.

7. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent containing a predominating amount of hydrocarbons having less than three carbon atoms to separate asphalt, separating the asphalt from the oil and solvent, removing the solvent from the oil, extracting the substantially asphalt free oil with a paraifinoid fraction and a non-paraffinoid fraction and separating said fractions.

8. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon to separate' asphalt, separating the asphalt from the oil dissolved in said solvent, chemically treating the oil dissolved in said solvent, removing the solvent from the treated oil, extracting said treated oil with a selective solvent to form a paraffinoid fraction and a non-paraflinoid fraction and separating said fractions.

9. A process as in claim 8 in which the selective solvent is sulphur dioxide.

10. A method of treating oil containing asphalt which comprises commingling said oil with a liquefied normally gaseous hydrocarbon containing a major portion of propane to separate asphalt, separating the asphalt from the oil dissolved in said solvent, chemically treating the oil dissolved in said solvent, removing the solvent from the treated oil, extracting said treated oil with a selective solvent to form a parafiinoid fraction and a non-paraffinoid fraction and separatingsaid fractions.

11. A process for the treatment of lubricating oil which comprises dissolving said oil in a liquefied normally gaseous hydrocarbon solvent, chemically treating the oil dissolved in said solvent, separating'the solvent from the treated oil, extracting the treated oil with a selective solvent to form a paraflinoid fraction and a non-paraffinoid fraction and separating said fractions.

12. A process as in claim 11 in which the selective solvent is sulphur dioxide.

13. A process for the treatment of lubricating oil which comprises dissolving said oil in a liquefied normally gaseous hydrocarbon solvent containing a major portion of propane, chemically treating the oil dissolved in said solvent, removing the solvent from the treated oil, extracting said treated oil with a selective solvent to form a paraflinoid fraction and non-paraflinoid fraction and separating said fractions.

-14. A process as in claim 13 in which the selective solvent is sulphur dioxide.

ULRIC B. BRAY.

CLAUDE -E. SWIFT. 

